Method of manufacturing inkjet head substrate

A method of manufacturing an inkjet head substrate that includes

• an energy generating element that generates energy for discharging ink and
• an ink supply port having
• a through portion that passes through the inkjet head substrate from a first surface thereof on which the energy generating element is disposed to a second surface thereof that is opposite to the first surface and
• a non-through portion that does not pass through from the first surface to the second surface,
• the non-through portion being disposed at a position closer than the through portion to the energy generating element in a region near the first surface, the method comprising:
• providing a substrate;
• disposing a mask on the first surface of the substrate, the mask including an opening that has a relatively large opening-width portion and a relatively small opening-width portion, in which the opening width is measured in a predetermined direction;
• and
• forming the through portion in the substrate at a position corresponding to the relatively large opening-width portion and the non-through portion in the substrate at a position corresponding to the relatively small opening-width portion by performing reactive ion etching on the substrate through the opening of the mask in a single operation.